The present invention relates to a probe structure for a scanning probe microscope.
Conventionally, a probe for the end of a cantilever of an atomic force microscope (AFM) has silicon or silicon nitride as a base material and the cantilever section is made using microfabrication technology such as lithography or etching. In particular, a tip of the probe is required to be made with a pointed tip as a probe for an atomic force microscope. As a specific manufacturing method, oxidation is performed. Thereafter, an oxide film is removed by etching and sharpening is carried out. In this case, the shape of a needle point is conical (pyramid shaped due to the crystal state) as shown in FIG. 4. (O. Wolter, Th Bayer, J. Greschner: “Micromachined silicon sensors for Scanning Force Microscopy” J. Vac. Sci. Technol. B9 (2), Mar./Apr. 1353-1357 (1991)).
As another probe for an AFM, there has also been proposed a deposition tip formed by irradiating an electron beam to a cantilever tip inside a vacuum chamber of a scanning electron microscope, and depositing carbon products on the irradiated section using an electron beam. A cylindrical tip can be formed, but it is weak against impact and has insufficient strength for use as an AFM tip.
Experiments have also been carried out using a multi-wall carbon nanotube as an AFM probe, which is formed of multiple tubes in which one to a few tens of layers of graphite type carbon are accumulated. However, in addition to the fact that processing to attach this carbon nanotube to the tip of an AFM cantilever is difficult, even if this is attached well, rigidity is low, which means that it is unsuitable for fixing to a side wall and to measurement of a stepped sample.
A cantilever probe of the above described silicon nitride or silicon material has a probe tip formed into a pointed cone (pyramid) as shown in FIG. 4, and this means that each time the probe is brought into contact with a sample in order to acquire an image there is abrasion by the probe tip, and variation in the probe tip diameter. Since image resolution of a probe microscope is basically determined by tip diameter, these images suffer from deteriorated resolution during measurement. Also, since it is not possible to detect the variation of the tip diameter due to abrasion, it is not possible to obtain reproducibility in measurement, and LSI line width and precision are insufficient. A conventional probe is formed perpendicular to the cantilever surface 6, as shown in FIG. 1A, and, when scanning, the cantilever is in contact with and inclined upwards from the sample surface, which means that the probe contact angle is not perpendicular with respect to the sample surface. For this reason, a side wall angle is not correctly measured, and measurement of a vertically rising side wall is difficult. In this regard, the ideal probe direction is perpendicular with respect to the sample surface, as shown in FIG. 1B. A probe of the related art has a surface coated with a metallic film in order to give it conductivity, but since it is easy for the metallic film to become peeled off during scanning for image measurement, the metallic film is coated more thickly and there is a problem that the probe tip diameter is increased and image resolution is lowered.